1. Field of the Invention
The present invention generally relates to an automobile body structure and, more particularly, to an automobile rear body structure.
2. Description of the Prior Art
In general an automobile rear body structure comprises a rear frame assembly extending longitudinally of an automobile and a rear floor panel mounted thereon.
Japanese Laid-open Utility Model Publication No. 63-37332, published in 1988, discloses the use of a rear floor extending rearwardly from a rear passengers seat assembly so as to raise upwardly towards a rear package tray through an upwardly raised rear floor portion with a fuel tank positioned beneath the upwardly raised rear floor portion. This type of automobile rear body structure such as disclosed in the above mentioned publication is advantageous in that the space delimited beneath the upwardly raised rear floor portion and above a ground surface on which the automobile runs can be effectively utilized to accommodate the fuel tank of substantially increased capacity which may not be generally flat in shape and which may be manufactured so as to have a required rigidity.
Also, attempts have hitherto been made to increase the capacity of the rear trunk compartment in the automobile body structure. For this purpose, each of generally juxtaposed rear side frame is upwardly raised at a location generally about an associated rear wheel housing so that a rear end portion of the respective rear side frame which is immediately below the bottom of the rear trunk compartment can be lowered thereby to increase the capacity of the rear trunk compartment.
However, this prior art automobile rear body structure has been found to have a problem in that, since the fuel tank is partially enclosed by panel members positioned on respective sides of the automobile rear body structure so as to define left-hand and right-hand rear wheel housings, the fuel tank cannot be sufficiently protected from damage which may occur in the event of an end-to-side automobile collision in which the front of one automobile collides against one side of another automobile.
In addition, according to the prior art, each of the side frame has a uniform rigidity substantially over the entire length thereof. Therefore, in the event that an excessive impact is applied to the rear body structure as a result of an end-to-end automobile collision, not only may the side frames be damaged in their entirety, but the upwardly raised portion of each side frame clear from an associated rear wheel axle may also be excessively deformed to such an extent as to destroy a required suspension geometry according to which rear wheel suspension systems are laid out. Once the rear wheel suspension geometry is destroyed, the automobile will no longer run on the ground surface.